如何使用Jackson递归修改JsonNode的值 [英] How to modify the value of a JsonNode recursively using Jackson

问题描述

要求:
我想对JsonNode的内部值应用一些函数.函数可以是不同的，例如:-lowercasing一些值或将某些值附加到值上或将值替换为某些值.如何使用Jackson库实现该目标?请注意，JSON数据的结构可以不同，这意味着我想构建一个通用系统，该系统将接受一些路径表达式，这些路径表达式将基本上决定要更改的位置.我想使用函数式编程风格，以便可以将这些函数作为参数传递.

Requirements:
I want to apply some functions on the inner values of the JsonNode. The functions can be different eg:- lowercasing some values or appending something to the values or replace the values with something. How can I achieve that using Jackson library? Note that the structure of the JSON data can be different which means I want to build a generic system which will accept some path expression which will basically decide where to change. I want to use functional programming style, so that I can pass these functions as arguments.

例如:

输入:

{
  "name": "xyz",
  "values": [
    {
      "id": "xyz1",
      "sal": "1234",
      "addresses": [
        {
          "id": "add1",
          "name": "ABCD",
          "dist": "123"
        },
        {
          "id": "add2",
          "name": "abcd3",
          "dist": "345"
        }
      ]
    },
    {
      "id": "xyz2",
      "sal": "3456",
      "addresses": [
        {
          "id": "add1",
          "name": "abcd",
          "dist": "123"
        },
        {
          "id": "add2",
          "name": "XXXXX",
          "dist": "345"
        }
      ]
    }
  ]
}

在这种情况下，我必须具有两个功能，分别是lowercase()和convert_to_number().我想在每个"value"的所有"addresses"内的所有"name"属性上应用lowercase()函数. 对于convert_to_number()也是一样，但对于所有"dist"属性.

In this case I have to two functions basically, lowercase() and convert_to_number(). I want to apply lowercase() function on all the "name" attribute inside all the "addresses" of each "value". same goes for convert_to_number() , but for all the "dist" attribute.

因此，基本上JSON表达式将类似于以下函数:

So, basically the JSON expressions will be something like below for the functions:

lowercase() : /values/*/addresses/*/name
convert_to_number() : /values/*/addresses/*/dist

输出:

{
  "name": "xyz",
  "values": [
    {
      "id": "xyz1",
      "sal": "1234",
      "addresses": [
        {
          "id": "add1",
          "name": "abcd",
          "dist": 123
        },
        {
          "id": "add2",
          "name": "abcd3",
          "dist": 345
        }
      ]
    },
    {
      "id": "xyz2",
      "sal": "3456",
      "addresses": [
        {
          "id": "add1",
          "name": "abcd",
          "dist": 123
        },
        {
          "id": "add2",
          "name": "xxxx",
          "dist": 345
        }
      ]
    }
  ]
}

客户代码:

JsonNode jsonNode = ...
applyFunctionsRecursivelyBasedOnExpr(JsonNode jsonNode, String expr, Function )

推荐答案

正如@MichalZiober在他的回答中指出的那样， JsonPath 提供了比Jackson更强大的API， 当您需要执行基于JSON路径的操作时.

As @MichalZiober in his answer already pointed out, JsonPath offers a much more powerful API than Jackson, when you need to do JSON-path-based operations.

使用方法

Using methods JsonPath.parse and DocumentContext.map you can solve your problem in just a few lines:

import java.io.File;
import com.jayway.jsonpath.Configuration;
import com.jayway.jsonpath.DocumentContext;
import com.jayway.jsonpath.JsonPath;

public class Main {

    public static void main(String[] args) throws Exception {
        File file = new File("input.json");
        DocumentContext context = JsonPath.parse(file);
        context.map("$.values[*].addresses[*].name", Main::lowerCase);
        context.map("$.values[*].addresses[*].dist", Main::convertToNumber);
        String json = context.jsonString();
        System.out.println(json);
    }

    private static Object lowerCase(Object currentValue, Configuration configuration) {
        if (currentValue instanceof String)
            return ((String)currentValue).toLowerCase();
        return currentValue;
    }

    private static Object convertToNumber(Object currentValue, Configuration configuration) {
        if (currentValue instanceof String)
            return Integer.valueOf((String)currentValue);
        return currentValue;
    }
}

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